Field of the Invention
The present invention relates to a base isolation floor structure that is used, for example, as a floor structure, such as a free access floor, and operates a base isolation function against vibration and displacement of a building on earthquake or the like.
Description of the Conventional Art
Examples of the ordinary base isolation floor structure include a base isolation floor structure 2 shown in FIG. 15 that is disposed on a flat floor surface 5a, which is formed on a sole plate 5 in the form of a flat plate laid on a foundation floor surface 3 formed of a concrete slab (see FIG. 10 of JP-A-2000-266115).
The ordinary base isolation floor structure 2 contains plural horizontally moving structures 4 (i.e., base isolation structure) that are provided horizontally movably on the floor surface 5a of the sole plates 5, and thereby vibration and displacement in the horizontal direction of the building caused by earthquake or the like are prevented from being transmitted directly to a floor board 6 fixed on the horizontally moving structures 4 and a free access floor or the like, which is not shown in the figure, disposed on the floor board 6.
The horizontally moving structure 4 of the ordinary base isolation floor structure 2 has a space S having an annular horizontal cross sectional shape between a convex spherical surface 10a of an inner member 10 and a concave spherical surface 12a of an outer member 12. The horizontally moving structure 4 is provided horizontally movably with respect to the floor surface 5a of the sole plates 5 through guidance of plural balls 8 (i.e., rolling members) disposed between the floor surface 5a and a bottom surface 10b of the inner member 10 and inside the space S.
An upper surface 12b of the horizontally moving structure 4 has the floor board 6 in the form of a flat plate placed thereon. The floor board 6 is fixed to the outer member 12 through screw engagement of an external thread of a bolt 14 and an internal thread 12c of the outer member 12. An upper surface 6a of the floor board 6 has an free access floor, which is not shown in the figure, placed thereon and fixed thereto.
In the ordinary base isolation floor structure 2, the floor board 6 can move freely in any direction within the approximately horizontal surface on the floor surface 5a through horizontal movement of the plural horizontally moving structures 4 fixed to the floor board 6 with respect to the floor surface 5a of the sole plates 5.